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This PDF file contains the front matter associated with SPIE
Proceedings Volume 6905, including the Title Page, Copyright
information, Table of Contents, Introduction (if any), and the
Conference Committee listing.
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On the propagation of radiation with a suitably resonant optical frequency through a dense chromophoric system - a
doped solid for example - photon capture is commonly followed by one or more near-field transfers of the resulting
optical excitation, usually to closely neighboring chromophores. Since the process results in a change to the local
electronic environment, it can be expected to also shift the electromagnetic interactions between the participant optical
units, producing modified inter-particle forces. Significantly, it emerges that energy transfer, when it occurs between
chromophores or particles with electronically dissimilar properties (such as differing polarizabilities), engenders hitherto
unreported changes in the local potential energy landscape. This paper reports the results of quantum electrodynamical
calculations which cast a new light on the physical link between these features. The theory also elucidates a significant
relationship with Casimir-Polder forces; it transpires that there are clear and fundamental links between dispersion forces
and resonance energy transfer. Based on the results, we highlight specific effects that can be anticipated when laser light
propagates through an interface between two absorbing media. Both steady-state and pulsed excitation conditions are
modeled and the consequences for interface forces are subjected to detailed analysis.
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We use an algebraic method to derive explicit expressions for the structure of paraxial modes in a cavity consisting
of astigmatic mirrors. The algebra is based upon the use of ladder operators that raise or lower the mode indices,
when acting on a mode function. We show that the method is also applicable when the mirrors perform a uniform
rotation about their axes. We also find expressions for the orbital angular momentum in these modes.
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This work started the dynamic singular optics, or real-time topological dynamics of developing singular light fields. We
have used the system "laser beam → photorefractive crystal LiNbO3: Fe" which generates slowly developing scalar or
vector random scattered singular light field (speckle patterns). It was investigated by elaborated technique of phase
reconstruction for a scalar field or real-time Stokes-polarimetry for reconstruction of a vector field ellipticity and
azimuth. It was shown the "life-story" of pair singularities from pre-nucleation up to after-annihilation states is realized
as 'local topological transition' with fully reversible scenarios. Applications of dynamic singular optics are discussed.
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Instead of the well-known line type of phase singularities in optical and coherence fields, we introduce a new concept of
what we call Vortex Sheet into singular optics. This vortex sheet has a surface topological structure, on which the phase
of the scalar optical or the coherence fields becomes undefined with zero amplitude. Some properties related to these
surface topological deformations, such as optical and coherence surface flow, are investigated both theoretically and
experimentally for the first time.
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We report holographic generation of higher-order Laguerre-Gaussian (LG) beams using a liquid crystal on silicon
spatial light modulator (LCOS-SLM) device. In our experimental set-up, a flat-top light beam was projected
on the LCOS-SLM to generate LG beams of various mode indices without changes of the optical system. Additionally,
the size of the holographic phase pattern was optimized for each beam to maximize the mode purity
of the obtained beam. Holographic generation of LG beams is easily influenced by a distortion of the optical
system and deviation of the phase setting from an ideal one. Nevertheless, we obtained high-quality LG beams
with an additional phase pattern on the LCOS-SLM for canceling the distortion of the optical system and with
calibration of the phase control voltage for precise expression of the phase patterns. Numerical analyses are
also performed for two-dimensional beam profiles to verify the quality of the obtained beams. Through fitting
the obtained profiles to theoretical ones, we calculate the correlation coefficients R between the observed and
fitted profiles to find that R > 0.95 for all beams and that the correlation coefficients behave similarly to the
theoretically estimated mode purities, facts indicating that the quality of the obtained LG beams is close to the
theoretical limit in our experiments.
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We present a method that enables the generation of arbitrary positioned dual-beam traps without additional
hardware in a single-beam holographic optical tweezers setup. By this approach stable trapping at low numerical
aperture and long working distance is realized with an inverse standard research microscope. Simulations and
first experimental results are presented. Additionally we present first steps towards using the method to realize
a holographic 4π-microscope. We will also give a detailed analysis of the phase-modulating properties and
especially the spatial-frequency dependent diffraction efficiency of holograms reconstructed with the phase-only
LCOS spatial light modulator used in our system. Finally, accelerated hologram optimization based on the
iterative Fourier transform algorithm is done using the graphics processing unit of a consumer graphics board.
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The Pancharatnam-Berry phase is a geometric phase associated with the polarization of light. We present novel optical
phase elements based on the space-domain Pancharatnam-Berry phase. Such elements can be realized using
inhomogeneous anisotropic micro and nanostructures, where the geometric phase is induced by spin-to orbital angular
momentum transfer. The elements are polarization dependent, thereby enabling multipurpose optical elements. Vectorial
vortices, and vectorial vortex mode transformation for a hollow waveguide are demonstrated. Manipulating of thermal
radiation by use of anisotropic micro and nanostructures is also investigated. We demonstrate an extraordinary coherent
thermal radiation from coupled resonant cavities; each of them supports standing wave surface polaritons.
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We outline the specifications of a portable Bio-photonics Workstation we have developed that utilizes just a single spatial light modulator to generate an array of up to 100 reconfigurable laser-traps with adjustable power ratios making 3D real-time optical manipulation possible with the click of a laptop mouse. We employ a simple patented optical mapping approach from a fast spatial light modulator to obtain reconfigurable intensity patterns corresponding to two independently addressable regions relayed to the sample volume where the optical manipulation of a plurality of nano-featured micro-objects takes place. The stand-alone Biophotonics Workstation is currently being tested by external partners with micro-biologic and chemistry expertise.
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The generalized phase contrast method (GPC) can produce a rich variety of optical landscapes from an incident flattop
beam. Here we show that the GPC can generate various intensity distributions directly from an incident Gaussian
illumination. This is illustrated by using GPC-based implementation of phase-only apertures that efficiently redirect the
available photons from an initial bell-shaped intensity distribution into desired configurations. GPC can reshape a
Gaussian beam into patterns having sharp intensity transitions and a flat phase profile in the bright regions with superior
energy efficiency over amplitude masks. Eliminating the initial Gaussian-to-flattop beamshaping requirement can be
beneficial for various applications employing GPC-based patterns.
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Propagating three-dimensional speckle fields are threaded by random networks of nodal lines (optical vortices).
We review our recent numerical superpositions of simulations of random plane waves modelling speckle
(O'Holleran et al. Phys. Rev. Lett. in press), in which the nodal lines and loops were found to have the fractal
structure of brownian random walks. We discuss this result, and its comparison with the discrete vortices of the
Z3 lattice model for cosmic strings. We argue that the scaling depends on the geometry of small vortex loops
and avoided crossings. The analytic statistics of these events, along with related singularities are discussed, and
the densities of vorticity-vanishing points and anisotropy C lines are found explicitly.
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We present a study of composite vortices in light beams using component beams with no integral topological
charge. We observed the same general features that are seen in when the component beams have an integral
topological charge [E.J. Galvez, N. Smiley, and N. Fernandes, "Composite optical vortices formed by collinear
Laguerre-Gauss beams," Proc. SPIE 6131, pp. 19-26, 2006.]. These are: (1) that new vortices appear at
distances from the beam that depend on the ratio of the intensity of the component beams, and (2) that the
angular location of the vortices depends on the phase difference between them. We also observed that some of
the vortices associated with fractional charge that did not follow the same dynamics.
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We propose a quantum theory of rotating light beams and study some of its properties. Such beams are
polychromatic and have either a slowly rotating polarization or a slowly rotating transverse mode pattern. We
show there are, for both cases, three different natural types of modes that qualify as rotating, one of which is a
new type not previously considered. We discuss differences between these three types of rotating modes on the
one hand and non-rotating modes as viewed from a rotating frame of reference on the other, thus resolving some
paradoxes mentioned recently.
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We investigate optical properties of semiconductor atoms by absorption and
emission spectroscopies. Each of 3PJ' - 3P°J transitions except for J'=0 (the total angular
momentum of the ground state) is confirmed in broad emission spectra in a hollow-cathode
discharge in which negative electrodes incorporate semiconductor atoms that are evaporated
in the discharge. For finer spectroscopies, the 3P1 - 3P°0 cyclic transition for laser cooling of
silicon atoms at 252 nm is investigated in absorption spectra with a single-frequency tunable
deep-UV coherent light source, which has a high potential for controlling their nuclear spins.
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Optical binding can be understood as a laser perturbation of intermolecular forces. Applying state-of-the-art QED
theory, it is shown how light can move, twist and create ordered arrays from molecules and nanoparticles. The
dependence on laser intensity, geometry and polarization are explored, and intricate potential energy landscapes are
exhibited. A detailed exploration of the available degrees of geometric freedom reveals unexpected patterns of local
force and torque. Numerous positions of local potential minimum and maximum can be located, and mapped on contour
diagrams. Islands of stability and other structures are then identified.
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Semiconductor nanowires are drawing more and more interest due to their numerous potential applications in
nanoelectronics devices [1,2], including interconnects, transistor channels, nanoelectrodes, or in the emerging application
areas of photonics [3], chemistry [4] and photovoltaics [5]. In this context, optical tweezers appear like a pertinent tool
for the manipulation and assembly of nanowires into complex structures.
It was previously shown that the near-field existing at the surface of a waveguide allows the micromanipulation of
nanoparticles and biological objects [6,7]. In this article, we investigate for the first time to our knowledge the motion of
silicon nanowires above silicon nitride waveguides. The nanowires in aqueous solution are attracted toward the
waveguide by optical gradient forces. The nanowires align themselves according to the axis of the waveguide and get
propelled along the waveguide due to radiation pressure. Velocities are up to 40 μm/s.
For a better understanding of the experimental results, the distribution of the electromagnetic field in the nanowire is
calculated using the finite element method. Then, the resulting optical forces exerted on the nanowires are calculated,
thanks to the Maxwell stress tensor formalism.
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Previous work has shown that single-beam gradient traps are unable to trap high index particles in fluids
where the index contrast is large. However, by changing the refractive index of the surrounding medium to
more closely match the index of refraction of the particle, trapping of high index particles is possible. We
report preliminary efforts to trap high index glass particles having indices of about 1.9. The experimental
trap stiffness data of polystyrene beads with radius 1.8 and 10 µm suspended in water is presented. The
next step is to trap high index particles as well as determine the trap stiffness for those particles having
diameters in the 3-10 μm range suspended in fluids having refractive indices in the range of 1.4 to 1.6.
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